1. Field of the Invention
The present invention relates to an agent for preventing and treating opacity of lens; more specifically, the present invention relates to an agent for preventing and treating opacity of lens, the agent comprising as effective ingredients specific organic germanium compound or the specific organic germanium compound together with aminoguanidine.
The present invention further relates to a highly effective agent for preventing and treating opacity of lens, the agent comprising a combination of a specific organic germanium compound and specific phenoxazine derivatives.
2. Prior Art
Lens of eyes is composed of as principle components about 65% of water and about 35% of protein, the ratio of protein contained in lens being higher than in other tissues. Under a variety of biological controls, than the protein in a high concentration, along with water inside cells, forms and maintains lens in hydrophilic colloidal state to retain transparency thereof. If lens which should be transparent happens to get opaque by some etiology, however, the quantity of light which reaches the retina decreases. Thus, visual acuity through the lens generally deteriorates, depending on the degree of opacity induced.
As the etiology of the incidence of opacity in the lens is diversified, it is quite difficult to discuss generally. One of the proposed mechanisms is such that the water-soluble, the membrane and the water-insoluble lens proteins described above, contain vast amounts of the SH group (thiol group), which are transformed into a S--S bond through a biological oxidative reaction, to form insoluble aggregated products, leading to the opacification of the lens. Another explanation is that the aforementioned proteins react with sugars non-enzymatically and irreversibly to form a reaction mixture called Amadori-products, of which reactions are general reactions between amino group of proteins and carbonyl groups of sugars, known as the Mailard Reaction. And this Mailard Reaction is considered to be a key reaction leading to aging. Such an explanation is considered to be one of the etiologies for causing opaque lenses.
The typical example of disease associated with an opaque lens is known as a cataract, which is classified into congenital cataract and an acquired one. The latter is further classified into senile cataract, traumatic cataract and diabetic cataract and others. In any type of cataracts, the formation of Amadori-products is considered to be a cause of lens opacities.